Core D will serve as the pathology section serving as the resource for the acquisition and tissue based evaluation of patient material (Project 3 and Core C), the development and implementation of immunohistochemistry (Projects 1,2,3,4 and Core C) and in situ hybridization studies (Projects 1,2 and 3). With available antibodies to the GA 733 antigen provided by Core B, Core D will perform and evaluate its expression in patient tumors prior to their entry to the vaccine trail as not all colonic carcinomas express this antigen. Core D will interact actively with all projects and Core C with detailed morphologic and immunohistochemical evaluation of antibodies to the GA733 antigen in both patient material and patient tumors grown in SCID mice. Additionally, Core D will evaluate the tissue reactivity of GA 733 directed antibodies from patients with ulcerative colitis, healthy donor, and colorectal cancer patients before and after vaccination (Project 4). Core D will provide histologic, immunohistochemical, and tissue based molecular biologic studies of skin specimens from mice and humans injected intradermally with Ad mEGP or AdGA733-2. In situ hybridization will be provided to distinguish humans from mouse tissue in SCID mice transplantation studies. Additionally, Core D will serve in the evaluation of mouse tissue for potential toxicity of adenovirus vaccines (Project 2).